/*
 *  Copyright 2016-2019 Netflix, Inc.
 *
 *     Licensed under the Apache License, Version 2.0 (the "License");
 *     you may not use this file except in compliance with the License.
 *     You may obtain a copy of the License at
 *
 *         http://www.apache.org/licenses/LICENSE-2.0
 *
 *     Unless required by applicable law or agreed to in writing, software
 *     distributed under the License is distributed on an "AS IS" BASIS,
 *     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *     See the License for the specific language governing permissions and
 *     limitations under the License.
 *
 */
package com.netflix.hollow.api.objects.provider;

import static java.util.Objects.requireNonNull;

import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Supplier;

interface Util {
    static <T> Supplier<T> memoize(Supplier<T> supplier) {
        AtomicReference<T> value = new AtomicReference<>();
        return () -> {
            T val = value.get();
            if (val == null)
                val = value.updateAndGet(v -> v == null ? requireNonNull(supplier.get()) : v);
            return val;
        };
    }
}
